updated 2/25/2010 1:17:05 PM ET 2010-02-25T18:17:05

A volatile natural gas and air mixture large enough to fill a professional basketball arena had accumulated in tight quarters in a Connecticut power plant shortly before an explosion killed six workers, a federal safety investigator said Thursday.

Donald Holmstrom, of the U.S. Chemical Safety Board, said the practice of cleaning pipes at the under-construction power plant, known as a "gas blow," put 400,000 cubic feet of gas mixed with air into an area close to the plant's power block, and near many ignition sources.

The Feb. 7 explosion ripped apart the nearly completed 620-megawatt Kleen Energy Systems plant as workers for O&G Industries Inc. purged the gas line. The cause of the blast has not been determined.

Holmstrom said the practice of venting gas near buildings and workers is common, but called it "inherently unsafe." The board is strongly cautioning industry against the practice, and Holmstrom said it was working to develop ways to find safer alternatives.

He said that with the U.S. building more natural gas power plants, it was important to develop standards that will prevent such accidents in the future.

"Thousands and thousands of workers across the country will be involved in constructing these plants. The safety of these workers and the nation's energy independence are at stake as these gas-fired plants are built over the next 20 years," he said.

The U.S. Chemical Safety Board investigates serious chemical accidents. State and local authorities are conducting a separate investigation into whether there was any criminal negligence.

Holmstrom said deciding what ignited the gas is not a major focus of the federal safety investigation because there are so many possible sources at any work site. He said the best way of preventing future accidents is by preventing or controlling the release of natural gas.

Check back for more details on this developing story.

Copyright 2010 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Discuss:

Discussion comments

,

Most active discussions

  1. votes comments
  2. votes comments
  3. votes comments
  4. votes comments